How to compute Weather Underground data packet errors
From WeatherCat Wiki (Mahler)
If you noticing problems with your submissions to Weather Underground, your Internet service maybe unable to reliably send data to Weather Underground. You can confirm this by a simple check of the WeatherCat Status window and quick calculation. On the WeatherCat Status window you'll see the number of packets submitted to Weather Underground and how many were acknowledge (see illustration below:)
To determine the error rate, simply compute the percent of errors by subtracting the first number from the second and then dividing by the first:
(227670 - 227151)/227670
Multiplying by 100 to get a percentage results in an error rate of 0.2% for this particular example.